The major goal of our lab is to understand the molecular pathways involved in rigidity and force sensing at cell-matrix adhesions. In this grant we will explore how these pathways are altered in cancers related to depletion of tropomyosin and modifications of tyrosine kinases. Cancer cells typically show anchorage independence of growth and the cytoskeletal protein, tropomyosin (Tm), is depleted in many cancers. Further, restoration of normal Tm1 expression reverses the transformed phenotype. Recently our lab has shown that cell rigidity sensing depends upon local contraction units that displace matrix by 50-70nm and if a threshold force is exceeded rapidly, then rigid adhesions form. Local contraction units resemble muscle sarcomeres in size (~2 ?, function, and composition (actin, myosin II, alpha-actinin, tropomodulin and tropomyosin). After knockdown of Tm1, the local contractions are dramatically altered and the cells no longer sense the rigidity of fibronectin-coated substrates. Similarly, the knockdown of tyrosine kinases alters both rigidity sensing and the pattern of contractions that are measured from displacements of 500nm diameter PDMS pillars. We propose now to follow the time course of force dependence and the concentration and dissipation of adhesion and contractile proteins at the pillars. This will tell us the order of binding and provide clues about the molecular steps involved in the cycles of contraction and release. We will then address the question of how the tyrosine kinases involved in rigidity sensing (AXL, ROR2 and EGF) interplay with the early adhesion complexes as a function of the force on the complexes. Since tropomyosin inhibits transformation and tumor growth, we will determine how tropomyosin depletion alters the pattern of adhesion maturation on soft surfaces that enables transformation. Thus, we will be able to better understand the mechanochemical basis of transformation.
In many cancers, the cells are transformed such that they can grow on soft surfaces and lack the ability to sense substrate rigidity properly. Using nanofabricated force sensors, we have found that depletion of tropomyosin, a muscle protein that is depleted in many cancers, blocks rigidity sensing and alters the mechanosensing machinery. We now propose to determine how tropomyosin and the tyrosine kinases work together to sense rigidity normally and how those pathways are altered in cancer at a molecular level.
| Saxena, Mayur; Changede, Rishita; Hone, James et al. (2017) Force-Induced Calpain Cleavage of Talin Is Critical for Growth, Adhesion Development, and Rigidity Sensing. Nano Lett 17:7242-7251 |
| Saxena, Mayur; Liu, Shuaimin; Yang, Bo et al. (2017) EGFR and HER2 activate rigidity sensing only on rigid matrices. Nat Mater 16:775-781 |
| Lee, Nancy M; Erisken, Cevat; Iskratsch, Thomas et al. (2017) Polymer fiber-based models of connective tissue repair and healing. Biomaterials 112:303-312 |
| Cai, Haogang; Depoil, David; Muller, James et al. (2017) Spatial Control of Biological Ligands on Surfaces Applied to T Cell Activation. Methods Mol Biol 1584:307-331 |
| Cai, Haogang; Wolfenson, Haguy; Depoil, David et al. (2016) Molecular Occupancy of Nanodot Arrays. ACS Nano 10:4173-83 |
| Wolfenson, Haguy; Meacci, Giovanni; Liu, Shuaimin et al. (2016) Tropomyosin controls sarcomere-like contractions for rigidity sensing and suppressing growth on soft matrices. Nat Cell Biol 18:33-42 |
| Santos, Luís C; Blair, David A; Kumari, Sudha et al. (2016) Actin polymerization-dependent activation of Cas-L promotes immunological synapse stability. Immunol Cell Biol 94:981-993 |
| Meacci, Giovanni; Wolfenson, Haguy; Liu, Shuaimin et al. (2016) ?-Actinin links extracellular matrix rigidity-sensing contractile units with periodic cell-edge retractions. Mol Biol Cell 27:3471-3479 |
| Hu, Junqiang; Gondarenko, Alexander A; Dang, Alex P et al. (2016) High-Throughput Mechanobiology Screening Platform Using Micro- and Nanotopography. Nano Lett 16:2198-204 |
| Yao, Mingxi; Goult, Benjamin T; Klapholz, Benjamin et al. (2016) The mechanical response of talin. Nat Commun 7:11966 |
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